1. Field of the Invention
The invention relates to an inflatable packer device, such as a packer, bridge plug, or the like, for use in a subterranean well bore, and a method of using same.
2. Description of the Prior Art
Inflatable packers, bridge plugs, and the like have long been utilized in subterranean wells. Such inflatable tools normally comprise an inflatable elastomeric bladder element concentrically disposed around a central body portion, such as a tube or mandrel. A sheath of reinforcing slats or ribs is typically concentrically disposed around the bladder, with a thick-walled elastomeric packing cover concentrically disposed around at least a portion of the sheath, typically a central portion of the sheath. Pressured fluid is communicated from the top of the well or interior of the well bore to the bore of the body and thence through radial passages, or around the exterior of the body, to the interior of the bladder.
Normally, an upper securing means engages the upper end of the inflatable elastomeric bladder and reinforcing sheath (if included in the design), sealably securing the upper end of the bladder relative to the body, while a lower securing means engages the lower end of the bladder and reinforcing sheath, sealably and slidably securing the lower end of the bladder for slidable and sealable movement on the exterior of the body, in response to the inflation forces.
With inflatable packers of this type, it has been observed that the exposed anchor section of the packer prematurely inflates prior to the other sections of the packer which are reinforced against expansion by an elastomeric packing cover element. When an exposed portion, such as the upper exposed anchor section of the bladder, inflates, the lower end of the bladder moves upwards relative to the body, and the exposed portion inflates until it meets the wall of the well bore, which may be cased or uncased. If well bore is uncased, the well bore will have a wall, and if the well bore is cased, the wall of the well bore will be the interior of the casing.
Although not fully understood, as the inflation begins to propagate downward and the reinforced portions of the bladder begin to inflate, the bladder has a propensity to pinch around the exterior of the body, creating a seal that prevents the effective communication of further fluid to the lower portions of the bladder. As the upper portion of the bladder above the seal continues to inflate, a convoluted fold forms in the bladder at the point of the seal, thus entrenching the seal.
The seal prevents or obstructs passage of the pressured fluid, employed for inflating the inflatable bladder, from reaching the lower portions of the bladder. Further, if the bladder is successfully inflated, the convoluted fold often remains in the bladder. During deflation, this fold can similarly pinch and seal around the body, obstructing the communication of fluid out of the lower portions of the bladder and thereby preventing complete deflation of the bladder. This nonuniform axial inflation of the bladder also causes the ribs in the sheath to cut into the bladder.
Applicant is aware of the following prior art: U.S. Pat. Nos. 4,781,249, 4,897,139, and 4,979,570, which are related in subject matter.
The present invention addresses the nonuniform axial inflation and rib-cutting problems set forth above by providing an inflatable packer device and method of use which provides a series of shape controlling means disposed along the length of the bladder to cause substantially uniform axial inflation of the bladder.